Colin P.R. McCarter

Experimental hydrological forcing to illustrate water flow processes of a subarctic ladder fen peatland

Department of Geography and Environmental Management, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada, N2L 3G1 Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada, N2L 3G1 Correspondence Colin P. R. McCarter, Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1. Email: mccarterc@gmail.com

Nutrient and mercury transport in a sub-arctic ladder fen peatland subjected to simulated wastewater discharges

Safely treating wastewater in remote communities and mining operations in sub-arctic Canada is critical to protecting the surrounding aquatic ecosystems. Undisturbed fen peatlands have been used to minimize the release of contaminants to the aquatic ecosystems; however, there is a limited understanding of wastewater transport or polishing in undisturbed fen peatlands. To elucidate these processes, a small (9800m2, ~250m long) ladder fen was continuously injected with a wastewater surrogate derived from a custom fertilizer blend and 38m3day-1 of water for 51days. The simulated wastewater included sulphate (27.2mgL-1), nitrate (7.6mgL-1), ammonium (9.1mgL-1), phosphate (7.4mgL-1), and chloride (47.2mgL-1). Major ion, total mercury (THg) and methylmercury (MeHg) pore water concentrations were measured throughout the study period. No wastewater contaminants were detected in the site outlet (~250m down-gradient) and most wastewater contaminants, except for SO42- and Cl-, remained relatively immobile. Within the SO42- plume, MeHg and THg concentrations became highly elevated relative to background (up to 10ngL-1, ~ three to five-fold increase) and MeHg comprised 60-100% of dissolved THg in the pore water. No MeHg or THg was exported at the outflow. The large increase in THg cannot be solely accounted for by the increase in MeHg and was likely due to enhanced decomposition of the peat substrate by increased microbial activity due to electron acceptor loading. Since the added nutrients were effectively transformed, sequestered or otherwise removed from pore waters in this experimental system, it appears that fen peatlands have a large capacity to safely treat residential wastewater nutrients; however, the inadvertent increases in THg and MeHg require further investigation and potential management.

Competitive transport processes of chloride, sodium, potassium, and ammonium in fen peat

There is sparse information on reactive solute transport in peat; yet, with increasing development of peatland dominated landscapes, purposeful and accidental contaminant releases will occur, so it is important to assess their mobility. Previous experiments with peat have only evaluated single-component solutions, such that no information exists on solute transport of potentially competitively adsorbing ions to the peat matrix. Additionally, recent studies suggest chloride (Cl-) might not be conservative in peat, as assumed by many past peat solute transport studies. Based on measured and modelled adsorption isotherms, this study illustrates concentration dependent adsorption of Cl- to peat occurred in equilibrium adsorption batch (EAB) experiments, which could be described with a Sips isotherm. However, Cl- adsorption was insignificant for low concentrations (<500 mg L-1) as used in breakthrough curve experiments (BTC). We found that competitive adsorption of Na+, K+, and NH4+ transport could be observed in EAB and BTC, depending on the dissolved ion species present. Na+ followed a Langmuir isotherm, K+ a linear isotherm within the tested concentration range (~10 - 1500 mg L-1), while the results for NH4+ are inconclusive due to potential microbial degradation. Only Na+ showed clear evidence of competitive behaviour, with an order of magnitude decrease in maximum adsorption capacity in the presence of NH4+ (0.22 to 0.02 mol kg-1), which was confirmed by the BTC data where the Na+ retardation coefficient differed between the experiments with different cations. Thus, solute mobility in peatlands is affected by competitive adsorption.

The effect of compression on Sphagnum hydrophysical properties: Implications for increasing hydrological connectivity in restored cutover peatlands: The effect of compression on Sphagnum hydrophysical properties

Department of Geography and Environmental Management, University of Waterloo, Waterloo, Ontario, Canada Department of Physical & Environmental Sciences, University of Toronto, Scarborough, Ontario, Canada Correspondence Tasha‐Leigh Gauthier, BES, University of Waterloo, 200 University Ave W, Waterloo, Ontario, Canada. Email: tgauthier@uwaterloo.ca Funding information NSERC Collaborative Research & Development Grant with the Canadian Sphagnum Peat Moss Association, Grant/Award Number: 437463‐2012